Baking oven



MY'ZS, 1936 D. HoULls 2,041,930

BAKING OVEN .May 26, 193s.

l.. D. HoULls 2,041,930

BAKING OVEN Filed sept. 7,' 1934 2 sheets-sheet 2 un? m INVENITR l Lau/.r D. ou//f ATTORNEY Patented May 26, 1936 UNIT-ED STATES PATENT oFllcE BAKING GVEN Louis D. nouns, seattle, wash.

Application September 7, 1934, Serial No. 743,045

5 Claims.

This invention relates to new and useful improvements in baking ovens.

One object of the invention is'to provide an improved baking oven which may be fired by fuel or Diesel oil, or natural or artificial gas.

An important object of the invention is to provide an improved ring or heating unit for a baking oven which has a maximum radiating surface and is so constructed that overheating, and resultant burning out of the system, is prevented.

Another object of the invention is to provide an improved firing unit for a baking oven which includes means for automatically recirculating a portion of the gases after they have cooled to some extent due to their rst circulation through the unit, this recirculation of thecool gases serving to prevent overheating of the heating unit and being accomplished without the aid of an auxiliary recirculating fan.

Another object of the invention is to provide an improved rebox having a, Venturi opening at its forward end through which the fuel to be burned is injected, said opening being constructed so as to Vent or suck in any cool gases which may be passed thereby.

A further object of the invention is to provide a heating unit for a baking oven including a rebox connected with a flue system through which the hot gases are circulated, and means for conducting the cooled gases, after their circulation, past the admittance opening in the lrebox, whereby said cooled gases are sucked into said rebox and reheated and recirculated; the entrance of said cool 'gases serving to prevent overheating of the rebox and burning out of the unit.

Still another object of the invention is to provide an improved flrebox having a Venturi opening in its forward end through which the fuel is injected, and having a conical outlet opening in its rear end, whereby the hot gases escaping from said opening are deflected inwardly so as to prevent them from contacting the metal walls of the flue system immediately upon escape from the iirebox; said opening being so constructed as to lili liti

also reflect a shadow in the immediate vicinity of the gas outlet, whereby firebox 'reflection is dulled and the forward portion ofthe flrebox is kept cooler.

A still further object of the invention is to provide an improved heating unit for a baking oven which is so constructed that the cooled gases are automatically recirculated, whereby the emciency is increased and the life of the unit prolonged.

Another object of the invention is to provide an improved heating unit including a iirebox which is so arranged that the flrebox is the only portion constructed ofl refractory material, the remainder of the unit being metal, thereby reducing the cost of manufacture and increasing radi- 5 ation and heating eiiiciency of the unit.

A construction designed to carry out the invention will be hereinafter described together with other features of the invention.

The invention. will be more readily understood l0 from a reading of the following specification and by reference to the accompanying drawings, in which an example of the invention is shown, and wherein:

Figure 1 is an isometric view of a baking oven lli constructed in accordance with the invention and having a portion broken away to show the ring unit, which is shown partly in elevation and partly in section,

Figure 2 is a transverse vertical sectional view, 20 taken on a line through the firebox, and

Figure 3 is a horizontal, cross sectional view, taken through the ues.

In the drawings, the numeral l0 designates an oven which may be of any desired shape or structure. The oven is shown as being substantially rectangular in shape and has the usual insulated walls l l and bottom l2. A vertically sliding door it" is provided in the front wall for easy accessibility to the interior of the oven and the usual revolving reel l Il is mounted within said oven. The articles to be baked are placed on the reel and the heating unit l5 is mounted on the floor of the oven beneath the reel.

The heating unit is an important feature of the invention and comprises a rebox I6 which is positioned at one end of the oven near the rear wall thereof, a sinuous ue l'l', a return passage it connecting the end of the flue with the inlet opening of the flrebox and an outlet riser i9 i0 communicating with the passage i8 for the escape of the hot gases, as will be hereinafter described.

The rebox it is constructed of two tubular sections A and B. The section A forms themain portion of the box, while the section B, which 4,5 is at the inner end of the section A, is slightly smaller in diameter and has a frusto-conical end, whereby the outlet of the rebox is reduced (Fig.- ure 3). The firebox is lined with refractory material, such as plastic brick, or the like. The outer end of the section A is provided with a small Venturi openingv 20 which receives the nozzle 2l o f the burner 22.

The burner may be of any suitable structure and may either burn oil or gas as desired. The

force of the blower (not shown) of the burner is suillcient to mix the oil or gas being injected with a certain amount of oxygen and force this mixture through the Venturi opening 2r] into the iii-ebox, in which it is completely burned and then expelled therefrom through the reduced opening at the inner end of the section B.

The flue Il has on one end a member l'l' enlarged and engaging over the inner end o1 the iirebox I6 and the hot gases are expelled thereinto. 'I'he member l1' is enlarged to prevent the extremely hot gases contacting the same and excessively heating the pipe and burning it out. The gases do not directly strike the flue i1 or the enlarged member Il' until the force of the gases has been considerably lessened. The enlarged member is connected to the ue i1 by a reducing nipple or collar I'. 'I'he flue comprises a plurality of longitudinal tubular metal pipes 23 which are suitably supported above the floor of the oven and are connected by elbows 23' at their ends so as to conduct the gases back and forth longitudinally over the oor oi? the oven. These pipes being of metal permit the heat from the gases passing therethrough to radiate upwardly within the oven. The discharge end of the flue I l is connected to the forward end of a transverse conductor 24 which comprises the return passage I8. This conductor extends rearwardly contiguous to the side wall Il of the oven through which the burner nozzle 2| extends.

By observing Figure 3, it will be seen that the conductor terminates in an enlarged housing 25 which is built around the outer end of the firebox so that the passage I8 communicates with the interior of the firebox I6 through the venturi 20. The rear end of the housing is connected with the outlet riser i9 which extends upwardly outside the rear wall of the oven.

In operation any suitable burner may be einployed. 'I'he force of the fan or blower within the burner is employed to inject the fuel with a certain amount of oxygen into the rebox. Substantially complete combustion takes place within the flrebox and the hot gases are ejected from the box into the enlarged pipe member il. The reduced inner portion of the rehcx prevents the hot gases from touching the metal wall of the pipe member il' immediately upon release from the flrebox, whereby the force of the gases is considerably vlessened before they contact the wall of said pipe'. The particular frusto-conical shape of this inner end also tends to reflect a shadow in the immediate vicinity of the outlet of the hot gases, which tends to kill rebox reflection and keep the outer end of the entire firing unit cooler.

The hot gases then travel from the rear of the oven through the :due I'l in the direction of the arrows in Figure 3. During their travel the heat of the gases is radiated from the walls of the said iiue and by the time said gases reach the passage I8, they have cooled considerably. These cooled gases pass rearwardly from the front of the oven through the conductor 24 and into-the enlarged housing 25 around the outer end of the rebox. 'I'he Venturi opening 20 in the outer end of the iirebox not only provides a mixture of fuel and oxygen entering the fire-box, but also vents or sucks in a portion of the cooled gases which are passing through the housing 25 on their way to the outlet riser i9 which extends upwardly from the rear of said housing. These cooled gases which are drawn into the ilrebox are, of course, reheated and recirculated through the flue unit. Such of the cooled gases which are not drawn into the ilrebox, escape through the outlet riser i9.

The constant entrance of the cooled gases into 'the iirebox keeps said box comparatively cool 5 and prevents overheating or burning out of the entire heating unit. thereby prolonging the life of said unit. The reheating of already cooled gases increases economy, without sacrificing eiiiciency and this is an important feature of the invention. The injection of the cooled gases into the hot flrebox brings about a heat exchange, whereby circulation is promoted and for this reason a recircuiating fan or blower is not required. This unit produces a maximum efilciency with a minimum of waste heat and its reedom from moving parts and auxiliary elements makes for its simplicity. It is pointed out that the rebox i6 is the only part of the entire unit which is of refractory materialfthe flue i1 being formed or uninsulated metal, whereby radiation and eilciency is increased.

The recirculation of the cooled gases is accomplished automatically, the Venturi opening being arranged to vent or suck in these gases which pass by said opening through the housing 25. It has been found that the usual blower or fan on the ordinary burner has sufiicient force tc maintain circulation. It would be possible, however, to employ the ordinary city gas pressure which is suiiicient to maintain the required circulation.

The description which has been given recites more or less detail of a particular embodiment of the invention, which is set forth as new and useful; however, I desire it understood that the invention is not limited to such exact details oi. construction, because it is manifest that changes and modifications may be made, within the scope of the appended ciaims. 40

What I claim and desire to secure by Letters Patent, is:

1. A heating unit for an oven comprising, a refractory iirebox having an inlet orifice at one end and a reduced frusto-conical outlet at its other end, means for injecting fuel into the box through the inlet opening. a metal flue connected with the outlet end of the box for receiving and circulating the hot combustion gases through an oven, the reduced frusto-conical end of the box preventing the hot gases from contacting the metal wall of the iiue immediately upon release from the box, and means for conducting the gasesfrom the iiue system past the inlet orifice of the rebox, whereby portions of these gases which have been cooled by circulation are sucked into the iirebox and reheated and reclrculated.

2. In a heating unit, a. iirebox comprising, a circulating ue, a refractory cylindrical box having an inlet orifice at one end for receiving a nozzle for injecting fuel into said box, the opposite end of the box having a reduced frustaconical outlet opening, whereby the force of the hot combustion gases ejected from the box is spent before contacting the wall of the iiue which a5 is connected to the outlet end of said firebox.

3. A heating unit for an oven comprising, a rebox including a cylindrical box having an orifice in its outer end for receiving a burner nozzle and having a reduced frusta-conical inner end, a flue connected to said inner end for circulating the hot combustion gases through an oven, means connected with the flue for conducting the gases after circulation through said system past the orifice -of the firebox, said orince being constructed so as to draw portions of these gases which have been cooled by circulation into the rebox, whereby these portions are reheated and recirculated through the flue, and an outlet conductor for naturally releasing the remainder of the cooled gases to the atmosphere. y

4. A heating unit for an oven comprising, a flrebox including a cylindrical body having an orifice in its outer end for receiving a burner nozzle and having a reduced frusto-conical inner end, a ue connected to said inner end for circulating the hot combustion gases through an oven, a conductor connected with the flue for conducting the gases after circulation through said system past the orifice of the lrebox, said orifice being constructed so as to draw portions of these gases which have been cooled by circulation into the rebox, whereby these portions are automatically reheated and recirculated through the ue without the aid of auxiliary means, and means connected with the conductor for the natural escape of the remainder of the cooled gases from said conductor to the atmosphere.

5. A heating unit for an oven comprising, a. sinuous circulating flue, a refractory irebox directly connected to one end of the iiue for discharging hot gases directly into the flue, said box having an inlet at one end and a reduced frustoconical outlet at the other end, said flue being so constructed that in cooperation with the reduced outlet of said box the hot gases are prevented from contacting the flue until the force thereof has been lessened, a burner extending into the inlet end of said box, and means for conducting heated currents from said iiue and discharging the same to the atmosphere to create a natural draft through said ues, the ue having a by-pass extending across the inlet end of said fire-box, whereby a. portion of said heated air currents are drawn into the inlet of said box for recirculation.

LOUIS D. HOULISc 

